<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>圆形</title>
    <style>
        /* 
            1.使用border
            2.使用宽高
        
         */
       /*  div{
            width: 0;
            height: 0;
            border: 100px solid red;
            border-radius: 50%;
        } */
        div{
            width: 100px;
            height: 100px;
            border: 1px solid red;
            /* border: 100px solid red;  */
            border-radius: 50%;
        }
    </style>
</head>
<body>
    <div></div>
</body>
</html>